1. Field of the Invention
The present invention relates to an arteriosclerosis examining apparatus for examining arteriosclerosis, in particular, arteriosclerosis obliterans.
2. Related Art Statement
There is known, as a sort of arteriosclerosis, atherosclerosis that is arterial atheroma caused by deposit of lipid, such as cholesterol, on inner walls of arteries. Since atherosclerosis causes stenosis of arteries, it is also called arteriostenosis, or arteriosclerosis obliterans. There is known an inferior-and-superior-limb blood-pressure-index measuring apparatus as an apparatus for examining arteriostenosis. This apparatus is disclosed in, e.g., Japanese Patent No. 3,140,007 or its corresponding U.S. Pat. No. 6,355,000. The blood-pressure-index measuring apparatus includes two inflatable cuffs that are adapted to be worn on an inferior limb and a superior limb of a living subject, calculates, as an inferior-and-superior-limb blood-pressure index, a ratio of one of a superior-limb blood pressure and an inferior-limb blood pressure to the other, and examines arteriostenosis based on the thus calculated inferior-and-superior-limb blood-pressure index.
More specifically described, examination of arteriostenosis based on inferior-and-superior-limb blood-pressure index is effected by comparing the index value with a predetermined reference value. For example, in the case where an inferior-and-superior-limb blood-pressure index is calculated by dividing an inferior-limb systolic blood pressure by a superior-limb systolic blood pressure, if the index value is greater than 0.9, it can be judged that the subject does not have arteriostenosis and, if not, it can be judged that the subject is suspected of having arteriostenosis.
In many cases, arteriostenosis occurs to inferior limbs of living persons. Hence, the inferior-and-superior-limb blood-pressure-index measuring apparatus is used for the purpose of examining arteriostenosis of inferior limbs. In fact, arteriostenosis may occur to other regions of living persons. However, the examination based on the inferior-and-superior-limb blood-pressure index cannot be used to diagnose or identify in which region arteriostenosis is present.
It is therefore an object of the present invention to provide an arteriosclerosis examining apparatus which can accurately examine arteriosclerosis of a living subject.
The above object has been achieved by the present invention. According to a first aspect of the present invention, there is provided an apparatus for examining arteriosclerosis of a living subject, comprising a pulse-wave detecting device which detects a pulse wave from a first portion of the subject; a stenosis-related-information obtaining means for obtaining, based on a shape of the pulse wave detected by the pulse-wave detecting device, stenosis-related information that changes in relation with stenosis of an artery of a second portion of the subject that is located upstream of the first portion of the subject in a direction in which blood flows in the artery; and a stenosis judging means for making, based on the stenosis-related information obtained by the stenosis-related-information obtaining means, a judgment about the stenosis of the artery of the second portion of the subject.
If the artery located upstream of the portion where the pulse-wave detecting device is worn has stenosis, the shape of the pulse wave detected by the detecting device changes in relation with the stenosis. Therefore, the stenosis-related-information obtaining means obtains, based on the shape of the pulse wave detected by the pulse-wave detecting device, the stenosis-related information that changes in relation with the stenosis, and the stenosis judging means makes, based on the stenosis-related information obtained, a judgment about the stenosis of the artery located upstream of the portion where the detecting device is worn. Thus, the present apparatus may be used such that the pulse-wave detecting device is worn on each one of different portions of the subject so as to make a judgment about stenosis of an artery located upstream of the each portion, or may employ a plurality of pulse-wave detecting devices which are adapted to be worn on different portions of the subject so as to detect respective pulse waves and make, based on those pulse waves, respective judgments about stenosis of respective arteries located upstream of those portions. In either case, the present apparatus can identify an arteriostenotic portion of the subject.
A waveform of the pulse wave detected by the pulse-wave detecting device may be deformed by noise such as arrhythmia or physical motion of the subject. This pulse wave is not appropriate for use in making a diagnosis on arteriostenosis. If stenosis-related information is obtained based on the inappropriate pulse wave, an appropriate diagnosis cannot be made on arteriostenosis.
Hence, preferably, the stenosis-related-information obtaining means comprises means for selecting, from a plurality of heartbeat-synchronous pulses of the pulse wave detected by the pulse-wave detecting device, at least one heartbeat-synchronous pulse whose waveform has an identifiable characteristic point; and means for obtaining the stenosis-related information based on the selected heartbeat-synchronous pulse.
According to this feature, the stenosis-related-information obtaining means selects, from the heartbeat-synchronous pulses of the pulse wave detected by the pulse-wave detecting device, a heartbeat-synchronous pulse whose waveform has an identifiable characteristic point, and the stenosis-related information is obtained based on the thus selected heartbeat-synchronous pulse. The stenosis-related information obtained based on the heartbeat-synchronous pulse whose waveform has the identifiable characteristic point is accurate information, and the stenosis judging means makes, based on the accurate stenosis-related information, a judgment about the stenosis of the artery located upstream of the portion where the detecting device is worn. Thus, the present apparatus can make an accurate diagnosis about arteriostenosis.
According to another feature of the first aspect, the stenosis-related-information obtaining means comprises a sharpness-degree determining means for determining a degree of sharpness of each of a plurality of heartbeat-synchronous pulses of the pulse wave detected by the pulse-wave detecting device; and an average-sharpness-degree calculating means for calculating an average of the respective degrees of sharpness of the heartbeat-synchronous pulses of the pulse wave determined by the sharpness-degree determining means, and the stenosis judging means makes the judgment about the stenosis of the artery of the second portion of the subject, based on a degree of sharpness of at least one heartbeat-synchronous pulse of the pulse wave determined by the sharpness-degree determining means, when a comparison value which is obtained by comparing the degree of sharpness of the at least one heartbeat-synchronous pulse, with the average sharpness degree calculated by the average-sharpness-degree calculating means, falls within a reference range.
According to this feature, the stenosis judging means makes the judgment about the stenosis of the artery, based on an average one of respective degrees of sharpness of respective heartbeat-synchronous pulses of the pulse wave detected by the pulse-wave detecting device. It can be said that an average degree of sharpness is derived from a heartbeat-synchronous pulse whose waveform is not deformed by noise or arrhthmia. Thus, the present apparatus can make an accurate diagnosis about the stenosis of the artery located upstream of the portion where the detecting device is worn.
According to a second aspect of the present invention, there is provided an apparatus for examining arteriosclerosis of a living subject, comprising a first-pulse-wave detecting device which detects, as a first pulse wave, a pulse wave from a first portion of the subject; a second-pulse-wave detecting device which detects, as a second pulse wave, the pulse wave from a second portion of the subject that is different from the first portion of the subject; a stenosis-related-information obtaining means for obtaining, based on a shape of the first pulse wave detected by the first-pulse-wave detecting device, first stenosis-related information that changes in relation with stenosis of a first artery of a third portion of the subject that is located upstream of the first portion of the subject in a direction in which blood flows in the first artery, and obtaining, based on a shape of the second pulse wave detected by the second-pulse-wave detecting device, second stenosis-related information that changes in relation with stenosis of a second artery of a fourth portion of the subject that is located upstream of the second portion of the subject in a direction in which blood flows in the second artery; and a stenosis judging means for making, based on the first stenosis-related information, and the second stenosis-related information, obtained by the stenosis-related-information obtaining means, a judgment about the stenosis of the first artery of the second portion of the subject, a judgment about the stenosis of the second artery of the fourth portion of the subject, and a judgment about a stenosis of a third, common artery that is located upstream of the first and second arteries in a direction in which blood flows in the third artery.
According to this aspect, the stenosis-related-information obtaining means obtains, based on the shape of the first pulse wave detected by the first-pulse-wave detecting device, the first stenosis-related information, and obtains, based on the shape of the second pulse wave detected by the second-pulse-wave detecting device, the second stenosis-related information. The first stenosis-related information reflects the stenosis of the first artery located upstream of the portion where the first-pulse-wave detecting device is worn, and the second stenosis-related information reflects the stenosis of the second artery located upstream of the portion where the second-pulse-wave detecting device is worn. Therefore, if the subject has arteriostenosis in a portion located upstream of the junction of the first and second arteries, both the first and second stenosis-related information values indicate arteriostenosis; if the subject has arteriostenosis in the first artery located downstream of the junction, only the first stenosis-related information value indicates arteriostenosis; and if the subject has arteriostenosis in the second artery located downstream of the junction, only the second stenosis-related information value indicates arteriostenosis. Thus, the stenosis judging means can make, based on the first stenosis-related information and the second stenosis-related information, a judgment about a stenosis of an artery located upstream of the junction of the first and second arteries, a judgment about the stenosis of the first artery located downstream of the junction, and a judgment about the stenosis of the second artery located downstream of the junction.
According to a preferred feature of the second aspect, the arteriosclerosis examining apparatus further comprises a pulse-wave-propagation-velocity-related-information obtaining device which obtains, based on the first pulse wave detected by the first-pulse-wave detecting device, first pulse-wave-propagation-velocity-related information that is related to a first velocity at which the pulse wave propagates in a fourth artery of the subject that includes the first artery of the third portion of the subject that is located upstream of the first portion of the subject.
Since pulse-wave propagation velocity lowers in an artery located downstream of an arteriostenotic portion, the length of the artery in which the velocity lowers increases as the distance of the stenotic portion from the portion where the first pulse wave is detected increases. Therefore, the amount of change of the pulse-wave-propagation-velocity-related information obtained by the pulse-wave-propagation-velocity-related-information obtaining device increases as the stenotic portion goes upstream along the artery from which the information is obtained. Thus, the stenotic portion can be identified based on the pulse-wave-propagation-velocity-related information obtained by the pulse-wave-propagation-velocity-related-information obtaining device.
According to the first aspect of the present invention, the stenosis judging means automatically makes a judgment about stenosis of an artery located upstream of the portion where the pulse-wave detecting device is worn. However, if the pulse wave detected by the pulse-wave detecting device is displayed by a display device, a medical person can make, to some extent, a judgment about arteriostenosis, based on the pulse wave displayed. However, as described above, the pulse-wave detecting device may detect an inappropriate pulse wave whose waveform is deformed by noise such as arrhythmia or physical motion of the subject. Based on the inappropriate pulse wave, an appropriate diagnosis cannot be made on arteriostenosis.
According to a fourth aspect of the present invention, there is provided an apparatus for examination of arteriosclerosis of a living subject, comprising a pulse-wave detecting device which detects, from a portion of the subject, a pulse wave including a plurality of heartbeat-synchronous pulses; a display device which displays a waveform of at least one heartbeat-synchronous pulse of the pulse wave detected by the pulse-wave detecting device; and a pulse-wave displaying means for operating the displaying device to display the waveform of the at least one heartbeat-synchronous pulse of the pulse wave when the waveform of the at least one heartbeat-synchronous pulse has an identifiable characteristic point.
According to this aspect, the pulse-wave displaying means operates the displaying device to display the waveform of the heartbeat-synchronous pulse of the pulse wave when the waveform of the heartbeat-synchronous pulse has an identifiable characteristic point. It can be said that a pulse wave whose waveform has an identifiable characteristic point is a pulse wave whose waveform is little deformed. Therefore, a medical person can make, based on the waveform of the pulse wave displayed by the display device, an accurate judgment about the stenosis of the artery located upstream of the portion where the pulse-wave detecting device is worn. The present apparatus may be used such that the pulse-wave detecting device is worn on each one of different portions of the subject so that the display device displays the pulse wave detected by the detecting device worn on the each portion and the medical person can make, based on the pulse wave displayed, a judgment about stenosis of an artery located upstream of the each portion, or may employ a plurality of pulse-wave detecting devices which are adapted to be worn on different portions of the subject so that the display device displays respective pulse waves detected by the detecting devices and the person can make, based on those pulse waves displayed, respective judgments about stenosis of respective arteries located upstream of those portions. In either case, the person can identify an arteriostenotic portion of the subject.
According to a fifth aspect of the present invention, there is provided an apparatus for examination of arteriosclerosis of a living subject, comprising a pulse-wave detecting device which detects, from a portion of the subject, a pulse wave including a plurality of heartbeat-synchronous pulses; a display device which displays a waveform of at least one heartbeat-synchronous pulse of the pulse wave detected by the pulse-wave detecting device; a sharpness-degree determining means for determining a degree of sharpness of each of the heartbeat-synchronous pulses of the pulse wave detected by the pulse-wave detecting device; an average-sharpness-degree calculating means for calculating an average of the respective degrees of sharpness of the heartbeat-synchronous pulses of the pulse wave determined by the sharpness-degree determining means; and a pulse-wave displaying means for operating, when a comparison value obtained by comparing a degree of sharpness of the at least one heartbeat-synchronous pulse of the pulse wave, determined by the sharpness-degree determining means, with the average sharpness degree calculated by the average-sharpness-degree calculating means, falls within a reference range, the display device to display the waveform of the at least one heartbeat-synchronous pulse of the pulse wave.
According to this aspect, the pulse-wave displaying means operates, when a comparison value obtained by comparing a degree of sharpness of a heartbeat-synchronous pulse of the pulse wave, determined by the sharpness-degree determining means, with the average sharpness degree calculated by the average-sharpness-degree calculating means, falls within a reference range, the display device to display a waveform of the heartbeat-synchronous pulse of the pulse wave. That is, the display device displays a waveform of a heartbeat-synchronous pulse having a near-average degree of sharpness. It can be said that a pulse wave having a near-average sharpness degree is a pulse wave whose waveform is not deformed by noise or arrhythmia. Therefore, a medical person can make, based on the waveform of the pulse wave displayed by the display device, an accurate judgment about the stenosis of the artery located upstream of the portion where the pulse-wave detecting device is worn. Like the apparatus according to the fourth aspect, the present apparatus can be used to detect respective pulse waves from different portions so that the medical person can make, based on those pulse waves, respective judgments about stenosis of respective arteries located upstream of those portions. That is, the medical person can identify an arteriostenotic portion of the subject.
In an exemplary embodiment, the pulse-wave-propagation-velocity-related-information obtaining device obtains, based on the second pulse wave detected by the second-pulse-wave detecting device, second pulse-wave-propagation-velocity-related information that is related to a second velocity at which the pulse wave propagates in a fifth artery of the subject that includes the second artery of the fourth portion of the subject that is located upstream of the second portion of the subject, and the apparatus includes a stenotic-portion identifying means for identifying, based on a comparison value obtained by comparing the first pulse-wave-propagation-velocity-related-information and the second pulse-wave-propagation-velocity-related information, with each other, a stenotic-portion of each of the first and second arteries.